Method and apparatus for gas shrouding of liquids

ABSTRACT

A liquid stream is protected from contamination during transfer between containers through establishment of a moving protective atmosphere around the liquid stream.

United States Patent [191 Pollard 1 METHOD AND APPARATUS FOR GAS SHROUDING OF LIQUIDS [75] inventor: Bernard Robert Pollard, Aliquippa,

[73] Assignee: Jones & Laughlin Steel Corporation,

Pittsburgh, Pa.

[22] Filed: Mar. 5, 1973 [21] Appl. No.: 337,999

[52] US. Cl. 164/66; 164/82; 164/259; 164/281 [51] Int. Cl.*....., B22D 11/10 [58] Field of Search 164/66, 259, 337, 82, 281

[56] References Cited UNITED STATES PATENTS 2.957.936 10/1960 Buggc ..l64/337X 51 Sept. 30, 1975 3,439,735 4/1969 Holmes 164/259 FOREIGN PATENTS OR APPLICATIONS 371.880 4/1932 United Kingdom 164/66 1,223,358 2/1960 France 164/66 22.298 11/1961 Germany 164/259 Primary Examiner-Robert D. Baldwin Attorney, Agent, or Firm-Gerald K. White; Thaddeus A. Zalenski 5 7 ABSTRACT A liquid stream is protected from contamination during transfer between containers through establishment of a moving protective atmosphere around the liquid stream.

18 Claims, 1 Drawing Figure U.S. Patent Sept. 30,1975

JIM! METHOD AND APPARATUS FOR GAS SIIROUDING OF LIQUIDS My invention generally pertains to a method and apparatus which provides a gaseous protective atmosphere around a liquid stream during transfer between containers. The invention has general applicability to any transfer process in which it is desired to protect the transferred material.

My invention comprises the use of an open-ended tube through which a protective gaseous atmosphere is continuously passed in a manner which causes the gas to exit from both ends of the tube. The liquid transfer stream is passed through the unconfined protective atmosphere which exits from the tube, then through the protective atmosphere within the tube, and then through the unconfined protective atmosphere which exits from the other end of the tube. In this manner, the entire stream is protected during transfer.

It is generally known in the art of transferring liquid steel between containers to provide a protective atmosphere for the purpose of preventing atmospheric contamination, such as oxidation, of the liquid steel. For example, various techniques are disclosed in US. Pat. Nos. 3,616,843 and 3,439,735 as well as in Austrian Pat. No. 228,418. However, the above patents, for one reason or another, lack the operational flexibility and combination of advantages associated with my invention. For example, US. Pat. Nos. 3,616,843 and 3,439,735 do not have the ability to be placed in and out of position while the liquid transfer stream is passing between the respective containers. This capability is extremely desirable from an operating standpoint for reasons which will be further illustrated. The above patents also do not provide for extreme ease of inspection of the liquid stream while it is being transferred. More over, the above protective devices are not of a nature that they may be easily removed or repaired and subsequently replaced during the transfer process. This ability is particularly important when the transfer process cannot be conveniently stopped due to overriding operational considerations. The device embodied by the Austrian patent also typifies problems inherent in prior art protective devices and methods. This device basically consists of attaching a refractory shroud to the initial container or vessel and immersing the lower portion of the shroud in the molten pool formed in the collecting vessel. It is obvious that the protective device cannot be readily removed and replaced or adjusted when required from time-to-time during operation of the transfer process. Furthermore, during emergency situations such as stream break-outs at the mold, nozzle chills, etc. the ceramic device must be broken in order to attain immediate access to the various containers. Upon subsequent resumption of the process, the ceramic shroud would either have to be replaced (a time consuming and extremely awkward procedure) or its use and benefits discontinued. Either alternative is undesirable. In addition, this technique does not provide protection for the top surface of the collected liquid in the collecting vessel.

It is thus an object of my invention to provide a method and apparatus which, although relatively simple in design and operation, possesses a combination of advantages when contrasted with the prior art. Such method and apparatus should be capable of providing adequate protection of the liquid stream from contamination and also be capable of being adapted to protect a wide range of stream sizes and reception vessel sizes and shapes.

It is an object of my invention to provide a technique which would permit immediate and full access to the liquid source opening of the initial transfer vessel. Such access could be obtained either through the opening between the open-ended tubular member and the vessel or by pivotally removing the open-ended tubular member without the necessity of first interrupting the moving liquid stream or destroying the protective device.

It is a further objective of my invention to provide a technique which will enable the liquid stream to be observed during the transfer process so as to provide the ability to visually detect conditions which may require corrective action.

It is yet another objective of my invention to provide a technique in which the transfer method may be interrupted and restarted in a simple manner without loss of the ability to continue contamination protection of the liquid stream. This objective may be accomplished either by suitably diverting the stream while the protective device is not in operating position or by temporarily discontinuing the flow of the liquid.

It is also an objective of my invention to provide a protective technique which is adapted for use with a plurality of successive transfer vessels.

It is an additional objective of my invention to have the capability of easily replacing the protective device or a portion thereof without interrupting the transfer process.

Additional objectives and advantages will be apparent to those skilled in the art from the following description of the invention.

The FIGURE illustrates an embodiment of the apparatus which is suitable for accomplishing the method of my invention. As will become more apparent in a later portion of the specification, the device comprises a first tubular member having open ends and dimensioned so as to be able to be positioned between a liquid exit opening of a liquid container and a liquid entry opening of a second container without contacting the containers. A second tubular member is attached to the first tubular member so as to form an interconnecting passageway between the tubular members. Positioning means are attached to the second tubular member to permit the first tubular member to be pivotally placed between the transfer containers and also to be removed from such position. A protective gas is passed through the second tubular member into the first tubular member in a manner which causes the gas to exit from both ends of the member.

The method of my invention generally comprises protecting a stream of liquid from contamination during transfer by shrouding it from the atmosphere through the use of a protective gas. In the process the stream is first passed through an unconfined protective gas which is generally moving in an opposite direction with respect to the stream. The stream then passes through a tube which contains and confines the protective atmosphere in a direction parallel to that of the stream. As the gas enters the tube in such a manner as to flow toward both open ends of the tube, it can be seen that the gas will flow in opposite directions while in the tube. This aspect is illustrated by use of arrows in the FIGURE. Thus, while passing through the interior of the tube, the stream will first encounter gas which flows countercurrent to the stream and then gas which flows concurrent with the stream. Upon exit from the tube interior, the gas flow will, of course, generally be in the same direction as the stream. As can be seen in the FIGURE, the second container is filled with the protective gas which issues from the lower end of the vertical tube. Such protective gas not only served to protect the liquid stream while in transit, but also functions to protect the surface of the collected liquid.

Thus, it may be seen that the invention provides a continuous gaseous shroud for the stream during the entire transfer process even though opposite gas flow is effected during certain portions of the shrouding process.

The use of the two unconfined shrouded areas of protection offer important advantages. First of all, the stream may be visually observed while the transfer process is being conducted. This is important from the standpoint of being able to effect quick and efficient corrective action when required by various process malfunctions. This advantage has obvious applicability when the transfer process involves the continuous casting of steel from a tundish. Here, it is often necessary to obtain access to the tundish nozzle to correct undesirable metal stream conditions such as frozen nozzles, reduced metal flow, nozzle chills, ragged streams, etc.

The continuous casting of metal is also useful to illustrate a further advantage of my invention. This advantage is that the inventive device may be selectively passed through the moving liquid stream without damage to the device whenever it is desired to either operatively position or remove the device. For example, during the initiation of transfer of metal from a tundish, there are often various problems associated with the nozzle before proper metal flow is initially attained. To correct such problems, access to the nozzle is required. Thus, during start-up, nozzle problems are first corrected and then the protective device is placed into position by moving the tube through the moving metal stream. This procedure provides for the creation of a stream having the desired flow characteristics and for subsequent protection of the stream. Of course, it a simple matter, to remove and replace .the device in the event that further access to the tundish nozzle is' required. By the same token, when casting malfunctions occur in the mold, it is often desirable or necessary to discontinue metal flow into the mold. When such procedure is required, the usual practice is to continue to permit metal to exit from the tundish. Such metal is diverted into a rubble box by means of a launder rather than permitting the metal to continue to enter the mold. As the device can rapidly be removed from its operating position by passing it through the stream, it is a simple matter to then quickly position the launder for the requisite diversion. The previously mentioned prior art devices simply do not have this capability for quick and flexible action.

The method obviously has utility in protecting liquid streams of any material that would suffer a deleterious effect without protection. It is particularly applicable to the transfer or casting of ferrous and non-ferrous metals in which it is desired to provide protection from oxidation. The reduction of non-metallic inclusions in steel by oxidation minimization is a typical example for which my process is adapted.

As would be expected by those skilled in the art, the effectiveness of the system is somewhat dependent upon gas flow rate and the type of liquid material being protected. Other factors include type of protective gas, tube dimensions (both the open-ended tube and the gas connection tube), tube geometry, and tube material. The choice of specific parameters from the above factors for a specific instance would be of a nature that would readily occur to a skilled artisan as they are basically a matter of engineering design.

Gas flow rates should, in general, be of a nature that the desired degree of protection can be attained. In this regard it is presently preferred to create a fairly low or slow flow rate in order to prevent possible aspiration of air in the unconfined areas of protection. It is probable that high flow rates which lead to excessive turbulent flow conditions should be avoided from the standpoints of air aspiration and cost of the protective gas.

Examples of suitable protective gases include argon, nitrogen, helium, other noble gases, and hydrocarbons such as natural gas, propane, coke oven gas, etc. It is also contemplated that admixtures of the above gases would be suitable for the purposes of this invention. Atomized hydrocarbon mists are also contemplated.

It should also be pointed out that tube dimensions and geometry can be varied greatly and still be within the scope of this invention. For example, the tubes may be of round, oval, square, rectangular, triangular, hexagonal, etc. configuration. The choice of configuration is dependent upon such factors as the shape of the liquid stream and desired gas flow characteristics as well as the shape of the respective transfer containers. It would also be within the scope of this invention to provide a tubular member which had a different configuration and/or opening area at each end of the tube.

The tube may be made of any suitable material which is of a nature and thickness, that will withstand contact with the liquid stream. When the stream is at a high temperature, such as liquid steel, suitable material would include, steel, other metals or alloys possessing elevated temperature resistance, as well as various refractory ceramic materials. If desired, composite metalrefractory tubes would also be suitable.

A trial utilizing the above described protective method was conducted for a continuous casting process in which a modified C 1018 steel was cast from a tundish into a mold. The steel had the following chemical analysis:

S Si .020 .23

Mn P .76 .013

TABLE EFFECT OF SHROUDING PRACTICE UPON CLEANLINESS LEVEL Cleanliness Argon Refractory Rating Shrouding Shrouded Unshrouded inclusions/sq.in. 0.01 0.06 0.25

oxygen: 0.0065 0.0101 0.0712

The FIGURE illustrates a preferred embodiment of an apparatus which is suitable for conducting the above described method. As may be observed, liquid stream,

20 is transferred from nozzle opening 11 in distribution container 11 through vertical open-ended tube member 14 of a generally circular configuration into collection container 13 where molten pool 34 is formed. Tubular member 14 is dimensioned so as to be able to be positioned between container 11 and container 13 without being placed in contact with the respective containers. A second tubular member, a rigid, horizontal gas connection tube 15, is attached to tubular member 14 at approximately its midpoint in a manner which forms an interconnecting passageway suitable for the passage of a protective gas between the respective tubular members. Positioning means 16 is connected to tube 15 in order to provide a means for pivoting the entire assembly. In this manner vertical tube 14 can be positioned between and/or removed from between container l1 and container 13. Positioning means 16 further comprises adjusting means 30, pivot means 31 and adjustment means 32. Adjusting means 30 permit connection tube, 15 to be rotated or twisted so that tubular member 14 may be ultimately tilted so as to change the vertical angle. Pivot means 31 functions to permit the entire tubular assembly to bepivoted about positioning member 16 whereby tubular member 14 may be pivotally moved so as to be able to alter horizontal placement or to move the tube in and out of its intended operating position. Of course, tubular member 14 could also be positioned by means which slidably or otherwise cause tubular member 14 to be positioned. Such means could be attached to either tubular member 14 or 15. Adjusting means 32 is a ball and socket arrangement which functions to permit ultimate changes in the vertical angular position of tube 14. Positioning member 16 is attached to support member 33 which in turn is attached to container 13. Protective gas is introduced into gas connection tube 15 through diffusion nozzle 17 which is fed from gas supply means 18. Diffusion nozzle 17 is desirably capable of creating a flow pattern and rate which will result in non-turbulent flow throughout the system. Such flow is considered to be preferred due to the possibility that a turbulent flow would cause aspiration of the ambient atmosphere and a consequent reduction in the protective capability of the system. The flow of gas throughout the system is depicted by the arrows on the drawing. It is also possible to introduce gas into tube 14 at a location or locations other than that depicted in the drawing. For example, when utilizing a gas which is heavier than air, i.e.; argon, one could conceivably find it advantageous to locate the introduction point nearer to the top of tube 14 in order to compensate for any tendency of the gas to travel in a downward direction. Conversely, when using a gas which is lighter than air, i.e.; nitrogen or helium, one could conceivably find it advantageous to introduce the gas at a point nearer to the bottom end of tube 14 so as to compensate for any tendency of the gas to travel in an upward direction.

In the case of metal transfer, distribution container 11 may be a tundish or a ladle and collection container 13 may be for example, a tundish or a mold. Various other combinations, of course, would be practical when the wide variety of metal processing techniques which involve the transfer of liquid metal are considered.

When the invention is used in combination with a tundish and mold as in a continuous casting process, the device may be attached either to the mold, tundish, or independently thereof. The choice of attachment is simply one which is dictated by design considerations. For example, when used with an oscillating mold systern, it has been found to be expedient to attach the device to the oscillating mold' as no problems have been observed in actual operation. Where using a ladle as the initial transfer container, it is probable that the device would be best attached to the ladle rather than to the tundish or mold. This is especially true if the ladle were used to feed a series of discrete molds because the .ladle would necessarily be moved sequentially and 1. A method for providing a protective gaseous atmosphere around a liquid stream during transfer between containers, comprising: i

a. passing said liquid stream from an exit opening of a first container through an unconfined protective gaseous atmosphere which is moving at least in a direction opposite to that of said liquid stream and which is located between said first container exit opening and an end of an open-ended tube;

b. further passing said liquid stream from said unconfined protective atmosphere into said tube and through a protective atmosphere which is confined by said tube in a direction generally parallel to that of said liquid stream;

c. further passing said liquid stream from the other end of the tube and said confined protective atmospherethrough an unconfined protective gaseous atmosphere which is moving at least in the same direction as that of said liquid stream and which is located between said other end of said open-ended tube and said second container entry opening;

d. further passing said liquid stream into the entry opening of said second container; and

e. selectively removing said open-ended tube together with said protective gaseous atmosphere from between said first and second containers and replacing said tube and said protective gaseous atmosphere thereafter.

2. A method for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 1, wherein:

said liquid stream is further collected under the influ ence of a protective gaseous atmosphere.

3. A method for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 1, wherein:

said liquid stream comprises a metal.

4. A method for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 3, wherein:

said liquid stream comprises steel.

5. A method for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 4, wherein:

said liquid stream of steel is continuously cast upon entry into said second container. ,4

6. A method for providing a protective gaseous atmo sphere around a liquid stream during transfer between containers as recited in claim 1, wherein:

said protective gaseous atmosphere is selected from the group consisting of argon, nitrogen, helium, a hydrocarbon, and admixtures thereof.

7. A method for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 6, wherein:

said protective gaseous atmosphere is argon.

8. A method for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 1, wherein:

said gaseous atmosphere is moving at a nonturbulent velocity.

9. Shrouding apparatus for providing a protective gaseous atmosphere around a liquid stream during transfer between containers in combination with distribution means which comprise a first container having a liquid exit opening for passing the liquid stream through said shrouding apparatus and into collection means which comprise a second container having a liquid entry opening, said shrouding apparatus comprising:

a. a first tubular member having open ends positioned between said liquid exit opening of said first container and said liquid entry opening of said second container without contacting said first and second containers so as to be able to observe said liquid stream during its transfer between said first and second containers and to provide access to said liquid exit and entry openings;

b. a second tubular member attached to said open ended first tubular member so as to form an interconnecting passageway suitable for the passage of a protective gas between said tubular members;

c. said second tubular member being rigid and connected to positioning means which comprise pivot means for placing and removing said first tubular member from between said liquid exit opening in said first container and said liquid entry opening in said second container; and cl. gas delivery n'teans for passing a protective gas into :tween containers as recited in claim 10, wherein:

said second tubular member is in a substantially horizontal position. 12. Apparatus for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 9, wherein:

said second tubular member is attached to said first tubular member at a location which is approximately at the mid-point of the length of said first tubular member.

13. Apparatus for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 10, wherein:

said positioning means further includes adjusting means for changing the vertical angular position of said first tubular member.

14. Apparatus for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 9, wherein:

said gas delivery means further comprises gas diffusion means for creating a non-turbulent gas flow through at least said first tubular member. 15. The combination of claim 9, wherein: said distribution means comprise a tundish-havingan outlet noz- 21c and said collection means comprise a mold. 16. The combination of claim 15, wherein: said collection means comprise a continuous casting mold.

17. The combination of claim 9, wherein:

said distribution means comprise a ladle having an outlet nozzle and said collection means comprise a tundish.

18. The combination of claim 9, wherein:

. said distribution means comprise a ladle having an outlet nozzle and said collection means comprise a mold. 

1. A method for providing a protective gaseous atmosphere around a liquid stream during transfer between containers, comprising: a. passing said liquid stream from an exit opening of a first container through an unconfined protective gaseous atmosphere which is moving at least in a direction opposite to that of said liquid stream and which is located between said first container exit opening and an end of an open-ended tube; b. further passing said liquid stream from said unconfined protective atmosphere into said tube and through a protective atmosphere which is confined by said tube in a direction generally parallel to that of said liquid stream; c. further passing said liquid stream from the other end of the tube and said confined protective atmosphere through an unConfined protective gaseous atmosphere which is moving at least in the same direction as that of said liquid stream and which is located between said other end of said open-ended tube and said second container entry opening; d. further passing said liquid stream into the entry opening of said second container; and e. selectively removing said open-ended tube together with said protective gaseous atmosphere from between said first and second containers and replacing said tube and said protective gaseous atmosphere thereafter.
 2. A method for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 1, wherein: said liquid stream is further collected under the influence of a protective gaseous atmosphere.
 3. A method for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 1, wherein: said liquid stream comprises a metal.
 4. A method for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 3, wherein: said liquid stream comprises steel.
 5. A method for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 4, wherein: said liquid stream of steel is continuously cast upon entry into said second container.
 6. A method for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 1, wherein: said protective gaseous atmosphere is selected from the group consisting of argon, nitrogen, helium, a hydrocarbon, and admixtures thereof.
 7. A method for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 6, wherein: said protective gaseous atmosphere is argon.
 8. A method for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 1, wherein: said gaseous atmosphere is moving at a nonturbulent velocity.
 9. Shrouding apparatus for providing a protective gaseous atmosphere around a liquid stream during transfer between containers in combination with distribution means which comprise a first container having a liquid exit opening for passing the liquid stream through said shrouding apparatus and into collection means which comprise a second container having a liquid entry opening, said shrouding apparatus comprising: a. a first tubular member having open ends positioned between said liquid exit opening of said first container and said liquid entry opening of said second container without contacting said first and second containers so as to be able to observe said liquid stream during its transfer between said first and second containers and to provide access to said liquid exit and entry openings; b. a second tubular member attached to said open ended first tubular member so as to form an interconnecting passageway suitable for the passage of a protective gas between said tubular members; c. said second tubular member being rigid and connected to positioning means which comprise pivot means for placing and removing said first tubular member from between said liquid exit opening in said first container and said liquid entry opening in said second container; and d. gas delivery means for passing a protective gas into and through said second tubular member and, thereafter, into said first tubular member so as to cause the protective gas to exit from the open ends of said first tubular member.
 10. Apparatus for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 9, wherein: said first tubular member is in a substantially vertical position.
 11. Apparatus for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recitEd in claim 10, wherein: said second tubular member is in a substantially horizontal position.
 12. Apparatus for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 9, wherein: said second tubular member is attached to said first tubular member at a location which is approximately at the mid-point of the length of said first tubular member.
 13. Apparatus for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 10, wherein: said positioning means further includes adjusting means for changing the vertical angular position of said first tubular member.
 14. Apparatus for providing a protective gaseous atmosphere around a liquid stream during transfer between containers as recited in claim 9, wherein: said gas delivery means further comprises gas diffusion means for creating a non-turbulent gas flow through at least said first tubular member.
 15. The combination of claim 9, wherein: said distribution means comprise a tundish having an outlet nozzle and said collection means comprise a mold.
 16. The combination of claim 15, wherein: said collection means comprise a continuous casting mold.
 17. The combination of claim 9, wherein: said distribution means comprise a ladle having an outlet nozzle and said collection means comprise a tundish.
 18. The combination of claim 9, wherein: said distribution means comprise a ladle having an outlet nozzle and said collection means comprise a mold. 